PS-B03-7: MAGNESIUM SULPHATE TREATMENT DURING HYPERTENSIVE PREGNANCY IMPROVES MATERNAL BUT NOT FETAL OUTCOMES IN RATS

Abstract

Objective: There has been a recent rise in the incidence of cardiovascular disease amongst women of child-bearing age and hypertensive disorders in pregnancy, in particular pre-eclampsia. Though it is frequently diagnosed, therapeutic interventions are lacking. Magnesium sulphate (MgSO4) is known to induce a vasodilatory effect via increased NO production and improved endothelial function and is currently used to prevent the progression to eclampsia and seizures from pre-eclampsia in the clinic. Magnesium homeostasis is also crucial during a healthy pregnancy and hypomagnesemia has been linked to cardiovascular disease. We hypothesised that MgSO4 may be used as a preventative therapeutic during hypertensive pregnancies in a rodent model of super-imposed pre-eclampsia. Design and Methods: Spontaneously hypertensive stroke prone (SHRSP) female rats were time mated. On gestational day (GD) 10.5 0.9% saline (SHAM, n = 10) or 750ng/kg/min of ANGII (n = 17) were administered via mini pump. A subset of ANGII and SHAM animals received daily 1% w/v MgSO4 drinking water from GD0.5 (n = 4/group; SHAM/ANGII+MgSO4). Blood pressure, cardiac function, and uteroplacental blood flow were measured by tail-cuff plethysmography and Doppler ultrasound pre-pregnancy (PP) and at GD6.5, 12.5, and 18.5. Urine samples were collected by metabolic cage at PP, GD6.5, and GD18.5 for measurement of proteinuria. Fetal and placental measurements were collected at sacrifice. Results: ANGII shows features consistent with SPE in humans via decreased stroke volume and elevated blood pressure alongside decreased fetal and placental weights vs SHAM (****p < 0.0001, **p < 0.01, *p < 0.05). Additionally, ANGII resulted in significantly altered fluid homeostasis and proteinuria vs SHAM (****p < 0.0001, ***p < 0.001, **p < 0.01). ANGII+MgSO4 showed a decrease in blood pressure vs ANGII (**p < 0.01). Treatment with MgSO4 had no significant effect on cardiac function, though there was a trend towards improvement in delta cardiac output. Neither ANGII nor additional MgSO4 altered indices of uteroplacental flow vs ANGII or SHAM. ANGII+MgSO4 exhibited a significant reduction in proteinuria vs ANGII (*p < 0.05) as well as improvements in fluid homeostasis. Both fetal and placental weights were significantly reduced in ANGII+MgSO4 vs SHAM (**p < 0.001) indicating a detrimental effect. Conclusions: These results suggest 1% w/v MgSO4 may be beneficial as a preventative therapeutic in pregnancies affected by super-imposed pre-eclampsia for maternal but not fetal outcomes. Further work is needed to elucidate the effects of MgSO4 in the context of hypertensive pregnancy.